In refusing to renew two mineral leases in northern Minnesota last Thursday, the federal government has, unexpectedly, gone much farther than simply frustrating the ambitions of a Chilean mining company.

Instead, it has launched a rare, two-year national environmental review to answer a question that has dogged Minnesotans for years: Is the state’s crown jewel, the Boundary Waters Canoe Area Wilderness, at such risk from copper-nickel mining that trillions of dollars worth of precious metals should remain in the ground for decades in order to protect it?

If federal regulators decide the answer is yes, they could place much of the watershed of the BWCA off limits to minerals exploration for the next two decades.

The affected zone — 234,000 acres of Superior National Forest land in the Rainy River watershed — is about 50 times bigger than the leases held by Twin Metals Minnesota. It holds some of Minnesota’s primary deposits of precious metals, but it also drains into a pristine and much-loved wilderness.

That would put the Boundary Waters on a par with other iconic places across the country, such as the Grand Canyon, Yellowstone National Park, and the Front Range in Montana, all of which been granted similar protections.

But it could cripple Minnesota’s nascent copper mining industry, especially if Gov. Mark Dayton follows through on his pledge to halt new mineral exploration on state-owned lands near the Boundary Waters.

Geologists say that about two-thirds of the known precious-metal mineral deposits in Minnesota lie within that watershed, and more than half are controlled by the state and federal governments.

The decision does not affect PolyMet Mining Corp., another company that has asked for a state permit to mine and process copper. Its operation, at an existing facility near Hoyt Lakes, would be built in an area that’s been heavily mined for years by the taconite industry and that drains to the St. Louis River and Lake Superior.

But it could affect a handful of other mining companies that have exploratory leases near the Twin Metals site on the Kawishiwi River near Ely.

“The [federal] actions will have a devastating impact on the future economy of the Iron Range and all of northeast Minnesota, eliminating the promise of thousands of good-paying jobs and billions of dollars of investment in the region,” Twin Metals said in statement last week.

But the decision also reflects a national shift in the way Americans value wilderness, in a way that cannot be measured in dollars, said Bonnie Keeler, a University of Minnesota scientist who studies the economics of natural systems.

“In the aggregate, how much better is the world because the Boundary Waters exists?” she said. “That’s what we are trying to figure out.”

‘This is their opportunity’

Starting as soon as next week, voices on both sides of the debate will have a chance to be heard.

The Bureau of Land Management, the agency that manages mining on federal lands, will open a 90-day public comment period on an environmental review that could take two years.

The Forest Service initiated that process by asking the secretary of the interior to withdraw the affected acres from mining activity for the next 20 years. Only Congress can ban development of federal lands permanently.

In the first phase, the public can propose what it wants the government to consider in the review — everything from the economic impacts on mining and recreation, to the potential risks to water and wildlife, to the psychic value of time in the wilderness.

“Whatever the people want studied, this is their opportunity to tell the agencies,” said Becky Rom, an Ely native and retired attorney who spearheaded the national Campaign to Save the Boundary Waters, the organization that fought for the review.

Once the federal agencies determine the scope of the questions, they will conduct a scientific environmental impact analysis to determine whether the lands should be withdrawn from potential mining.

That will include more public input from citizens, states, industry, tribes and environmental groups.

But it’s clear from the documents released last week that agencies are worried.

Hard rock mining of metals such as copper and nickel exposes ore and waste rock to air and water, generating acid mine drainage that leaches heavy metals and toxins into the water.

Government agencies already are struggling with 20,000 to 50,000 mines that now generate acid on federal lands, which have contaminated thousands of miles of streams and rivers, the Forest Service said.

Those mines “are known worldwide” for producing pollution that requires continuous management and perpetual water treatment, the agency said.

Though Twin Metals has proposed an underground mine, it still would be likely to generate acid mine drainage from its tailings basins and other activities, according to Forest Service documents.

Modern technologies

Deposits of copper are relatively abundant in the United States and many operating mines “are situated in arid or drier areas of the nation where their potential for environmental harm may be reduced,” the Forest Service said.

But the Boundary Waters Canoe Area, it said, “is irreplaceable.”

Twin Metals says modern technologies will allow it to develop a mine that protects the environment and water quality, and that it wants the opportunity to develop a plan that follows state and federal laws.

It’s already filed suit against the federal government arguing that refusing to renew its leases, which it and its predecessors have held since the 1960s, is illegal.

Last week it said that it will continue to pursue legal actions.

Whether the incoming Trump administration can — or would choose to — reverse the environmental review is unclear. Federal officials said Thursday that their decision is final and can be challenged only in court.

Rom pointed out that both Donald Trump and his nominee for interior secretary have publicly stated their support for federal control over federal lands. But both also supported using federal lands for natural resource development like oil drilling and mining.

Others say that halting the environmental review might not be easy for the new administration.

The BLM and the Forest Service laid out their reasoning very carefully, and backed it up with scientific research, said Kathryn Hoffman, an attorney with the Minnesota Center for Environmental Advocacy, a nonprofit law firm. The new administration “would have to go through the same process,” she said. Otherwise, “it’s open to legal challenge.”